Currently, soybean is transformed and regenerated using the cotyledonary node (“coty node”) method or the embryogenic callus culture (“callus”) method. The coty node method involves wounding the cotyledonary nodes on 5-7 day-old seedlings and co-cultivating the wounded seedlings with Agrobacterium tumefaciens for five days in the dark. Afterwards, plants are regenerated in tissue culture. The callus method involves particle bombardment of embryogenic tissue with DNA-coated carrier particles of inert material.
The coty node method is disadvantageous because it requires in vitro germination, precise wounding of the adaxial side of the cotyledonary node, which can result in poor reproducibility and non-germline transformation, which does not transmit the transgene to the progeny. Transformation efficiency typically ranges from 0.3 to 2.8%. The callus method is disadvantageous because it requires prolonged tissue culture, often yields complex insertion of genes into the plant genome, and may result in the regeneration of sterile plants.
The present invention seeks to provide an easier, more reproducible, more efficient, and more robust method of Agrobacterium-mediated transformation and regeneration of soybean. With the present invention, transformation efficiency typically ranges from 3.2 to 8.7%, with an overall efficiency of 4.9%. The method does not involve seed germination prior to explant preparation, nor does it involve deliberate and precise manual wounding. Other objects and advantages, as well as additional inventive features, will become apparent from the detailed description provided herein.